MIDTERM: STEM Flashcards
Functions of stem
►Conduction of materials
▶Support for aerial parts (leaves, fruits. flowers)
►Production of leaves, branches and new shoots
▶Food storage
►Photosynthesis (green stems)
External anatomy
- nodes
- internodes
- leaf axils
- buds
- apical/terminal buds
- axillary/lateral buds - leaf primordia
- bud primordia
- bud scales
- apical meristem
- region of elongation
- maturation region
- scars
joint-like structures where leaves develop
nodes
the spaces between nodes
internodes
angle formed by the leaf with the stem
leaf axils
growing or developing portions of the stem which give rise to shoots
2 types of buds
buds
apical/terminal buds
axillary/lateral buds
- formed at the tips/ends/apex of stems
- at the nodes or axils of the stems
apical/terminal buds
axillary/lateral buds
a typical bud consists of a mass of _____________
meristematic tissues
beginning of the leaves which surround the mass of cells of the bud
leaf primordia
beginnings of new buds
bud primordia
protect the apical meristem
bud scales
region of actively dividing cells
apical meristem
also has embryonic tissues
region of elongation
contain primary tissues (group of cells having common structure and function)
maturation region
marks the location of a certain part
3 types
scars
leaf scars
bud scars
vascular bundle scars
crescent-shaped or circular marks left by the fall of leaves; they are places at which the leaf stalks grew from the stem
leaf scars
ring of small narrow scars left by the falling away of the bud scales
bud scars
broken ends of vascular bundles which extend from the conducting tissues of the stem into the leaf stalk
vascular bundle scars
tiny raised pores in the stem for gas exchange
lenticels
TISSUES PATTERNS IN STEMS
stele
prostostele
siphonosteles
eusteles
- simplest form
- phloem surrounds the xylem
protostele
tubular with pith at the center
siphonosteles
- present in most plants
- primary phloem and primary xylem are in vascular bundles
eusteles
STEM CLASSIFICATION
LOCATION
- acaulescent
- caulescent
TEXTURE
- herbaceous
- woody
DIRECTION OF GROWTH
- erect
- ascending
- decumbent
- prostrate/procumbent
- creeping
- scandent/climbing
- with no obvious stem above the ground
- only the leaves are seen
eg. grasses
acaulescent
- with obvious stems above the ground, as in most stems
caulescent
- appear soft fleshy and green
- herbaceous plants often live only for a short period of time
herbaceous
- forms permanent woody tissues
- hard and usually covered with bark
woody
- ascends perpendicularly to the ground
- general direction of growth
erect
stem rises obliquely (slanting)
ascending
more or less reclining to the ground
decumbent
lying flat on the ground
eg. kamote
Prostrate/ procumbent:
- when closely pressed to the ground and rooting at the nodes
- with stolons
creeping
- stems ascend by means of a support offered by other plants or objects, whether by tendrils, rootlets or other means
scandent/climbing
INTERNAL STRUCTURE
herbaceous stems
woody stems
- (lack secondary growth)
✓ most ________ are herbaceous, while ________ are herbaceous or woody
✓ only the primary tissues are present (how many ____)
HERBACEOUS STEMS
monocots; dicots
6 PRIMARY TISSUES:
a. EPIDERMIS
b. CORTEX: contains parenchyma cells)
c. ENDODERMIS
d. VASCULAR BUNDLES: xylem-inner; phloem-outer
e. VASCULAR CAMBIUM: in between the xylem and in dicots only, where secondary growth arises
f. PITH: visible in dicots only
contains parenchyma cells
cortex
- xylem-inner
- phloem-outer
vascular bundles
- in between the xylem
- in dicots only, where secondary growth arises
vascular cambium
- visible in dicots only
- parenchyma cells inside the ring
pith
INTERNAL STRUCTURE
- vascular bundles do not have a definite arrangement (_______) in the cortex
- covered by a structure: _____________ thick-walled strengthening cells
- no pith (no definite distinction between cortex and pith)
- no secondary growth (secondary xylem and phloem, cork cambium, cork) occurs due to the absence of a ______________
scattered
vascular bundle sheath
vascular cambium
MONOCOTS
INTERNAL STRUCTURE
- growth in diameter is _________ on the increase in size of the primary tissues (epidermis, cortex, primary xylem and phloem)
- the greater part of the stems consist of _____________
- directly adjacent to the epidermis and surrounding the bundles are the ____________ and ____________ which strengthen and support the stem
- DISTINCT EPIDERMIS
dependent
parenchyma tissues
collenchyma and sclerenchyma tissues
MONOCOTS
INTERNAL STRUCTURE
- vascular bundles are arranged in an orderly _____ and are not scattered
- the _____ is present due to the circular arrangement of the vascular bundles
- ______________ is present which is visible between the xylem and phloem
ring
pith
vascular cambium
DICOTS
INTERNAL STRUCTURE
- it may be restricted to the individual bundles, or it may be continuous from bundle to bundle
- _________________ are poorly developed
- ___________ and ___________ function as supporting structures
- VASCULAR TISSUE ARRANGED IN A CYLINDER
secondary tissues
collenchyma and vascular fibers
DICOTS
INTERNAL STRUCTURE
WOODY STEMS
- aside from the primary tissues, there is the formation of ________________ which give rise to the ________ condition
- the __________ are in the form of ________________
secondary tissues
woody
conducting tissues
concentric circles/cylinders
SECONDARY TISSUES
a. ____________: layer of meristematic cells between the xylem and the phloem arranged in a cylinder
✓produces continuous layers of _______________ in the inner portion of the cylinder and ______________ in the outer area, therefore causing the mature stem to increase in thickness
Vascular cambium
secondary xylem cells
secondary phloem cells
INTERNAL STRUCTURE
b. _________________ : the inner derivative of the vascular cambium
- comprises about 90% of a typical tree
- cells present: _________ and ________________
- in concentric layers: each layer develops per year, thus are called __________
- in most trees water moves only in the _____________
- after one or two years, the tubes become filled with materials and soon die and become darker in color
Secondary xylem/wood
tracheids and vessels/vessel elements
annual rings
new annual ring
CLASSIFICATIONS OF WOOD
sapwood
heartwood
- wood in the outer rings of the xylem
- the transport of water and nutrients only occur in this area
sapwood
- older dark rings near the center/pith
- the portion wherein metabolites (gums, resin, oils, tannins) and other wastes are deposited and eventually clog up the xylary elements and cause the wood to become darker in color
- supports the tree
- more durable and more preferred for lumber
heartwood
3 TISSUES COMPRISING THE PERIDERM
phellogen/cork cambium
phellem/cork cells
phelloderm/secondary cortex
the meristem that produces the periderm
phellogen/cork cambium
- outer derivative of the cork cambium, occur in densely packed rows
- cells are dead, suberized, and function to waterproof, insulate, and protect the plant
phellem/cork cells
- inner derivative of the cork cambium, which is ______________
- cells are alive and not suberized
phelloderm/secondary cortex
parenchymatous
STRUCTURE OF WOOD
wood
annual ring
summerwood
springwood
- composed chiefly of cellulose and lignin
- a compound often associated with cellulose
wood
- outer band of each ring is made up of smaller and sometimes thicker-walled cells
- formed in the summer
summerwood
inner band of each ring is made up of rather large cells formed by the cambium in the spring
springwood
PHYSIOLOGY OF STEMS
- conduction of materials by the xylem
- transpiration pull
- cohesion-adhesion
- root pressure
- guttation
- conduction of materials in phloem
______ (function): upward conduction of water and dissolved nutrients (sap)
- minerals and food stored in the roots
what causes sap to go up?
_______________ are differentiated into tiny tubes which are like capillary tubes.
xylem
xylem cells
CONDUCTION OF MATERIALS BY THE XYLEM
_______________: loss of water through the stomates and lenticels due to:
a. __________: directly proportional rate of absorption
b. __________: indirectly proportional
c. __________: increases evaporation
___________: like a pull which causes water and sap to go up and replace the lost water
TRANSPIRATION PULL (pull from above)
a. temperature: higher temp = high rate of absorption
b. humidity: more humid = decreased rate “”
c. air current = presence of air current increases evaporation
transpiration
____________: holding together of like substances
cohesion
____________: holding together of unlike substances
adhesion
- water has a tremendous property of ___________, each molecule clinging tenaciously to several adjacent molecule
- when the leaves transpire (water evaporates from the ________), water is lost in the leaves and aerial parts molecule by molecule
- due to this water loss, the water in the ______________ will move up to the leaves
cohesion
stomates
vascular tissues
COHESION-ADHESION
- result of the _______________ of water into the vascular elements of the root
- generated by the ______________ from the soil to the xylem
- as long as water molecules continue to vacate transpiration sites, _______________ are pulled under tension and the root pressure then pushes water up (the pressure is generated by the active absorption of water)
osmotic uptake
active absorption
replacement molecules
ROOT PRESSURE (push from below)
- the excretion of droplets of water by plants from special openings called ___________ located at the edges or tips of leaves at the ends of veins
- occurs when humidity is _____, and so transpiration does not occur and water accumulates in the leaves (water is continuously being absorbed when environment is ____________)
- may also occur at night and during rainy season when evaporation is ____________
hydathodes
high
hypotonic
minimal
GUTTATION
Conduction of Materials in the Phloem
___________ (function): to distribute the products of photosynthesis via ____________
Mass flow/Pressure flow theory:
- flow of solutes in mass as a result of _____________ build up in the cells
- ____________: sites of food production in the plant (leaves)
- ____________: sites of use (other plant parts)
phloem
translocation
turgor pressure
source region
sink region
CONDUCTION OF MATERIALS IN THE PHLOEM
_____________: moves solutes (minerals) into the __________ of the phloem vessel
- As a result, there will be an increase in solute concentration in the sieve elements making them ____________
- Because they are __________, they will then attract water from nearby ___________ through __________
- When water moves into the ____________ of the phloem, ____________ builds up in those cells
active transport
sieve tubes
hypertonic
xylem vessels
osmosis
sieve elements
turgor pressure
- This will cause water and solutes to move into the next cell whose solute concentration is ______, until they reach the ___________. This is called ________.
- Water then moves out of the _________ and also goes into the _________ or re-enters the ________
lower
sink regions (regions of use)
bulk flow
sieve tubes
sink regions
xylem vessels
Meristems contain cells that usually
- are SMALL in size
- have THIN cell walls
- contain little or NO VACUOLE
- ______________ produce stem and leaf tissues (_____________)
- Apical meristem can switch to a ____________ and produce flowers
- Switch can be triggered by day length, temperature, and developmental stage
________: can be viewed as a series of concentric rings of various tissues
Shoot apical meristems
vegetative structures
floral meristem
stems
- External layer of cells
- Covered with a cuticle to reduce water loss
- May contain _______ and _______
- In woody plants this is replaced by a _______
- provides a stronger external surface
- more resistant to damage
- protective layer
stomata
trichomes
cork layer
EPIDERMIS
Functions of the
epidermis
- prevent water loss
- protect against invasion by pathogens
- protect internal tissues
